RESET Control

The STK600 controls the RESET signal to the target AVR. Under normal operation, the RESET line is held in an inactive, high state (pull-up to VTG).

The RESET jumper

The RESET jumper connects the RESET pin on the target AVR to the STK600. When the RESET jumper is mounted, STK600 controls the RESET signal. When the RESET jumper is not mounted, the RESET signal is disconnected. This latter is useful for prototyping applications with an external reset system.

The RESET jumper must always be mounted when High-Voltage programming an AVR device. If using an external reset system, it must allow the reset line to be controlled by the STK600 during programming.

The RESET button

STK600 has a reset button that resets the target AVR when being pushed. The button has no function if the RESET jumper is not mounted.

RESET signal on AUX header

The target AVR's RESET signal is accessible on the AUX header. This pin can be used to apply an external RESET signal. When applying an external reset signal, the reset jumper must be removed.

12V Programming Voltage

During High-Voltage Programming, STK600 applies 12V to the AVR’s RESET line. Thus, an external reset circuit not capable of handling this must be disconnected before High-Voltage programming the AVR.

External RESET de-coupling

When connected to an external system, there is often an external pull-up resistor and a capacitor connected to the reset line. A typical reset connection is shown below.

If the external pull-up resistor is too strong (i.e << 4.7kOhm), STK600 may not be able to pull the RESET line low.

See also: Reset Line when programming an external target.